Hydrogen-powered cars are based on fuel cells that store hydrogen, or H2 gas, inside a material called a polymer exchange membrane. The fuel cell contains two electrodes: an anode (negative side) and a cathode (positive side). At the anode, the H2 molecules are split into protons and electrons. The protons pass through a polymer exchange membrane, while the electrons are unable to pass through this membrane and thus have to flow in a different direction. This creates a current of electricity by which the car is powered.